Foliar Application of SeNPs for Rice Biofortification: a Comparative Study with Selenite and Speciation Assessment

Abstract

A significant portion of the global population lacks access to a balanced diet, leading to widespread micronutrient deficiencies. Selenium (Se) deficiency affects approximately 1 billion people worldwide, and agronomic biofortification of food crops using inorganic Se fertilizers or Se nanoparticles (SeNPs) has emerged as a potential solution. However, to ensure food safety, it is critical to assess whether nonbioavailable or toxic Se species are formed when SeNPs are introduced into plants. In this study, pot experiments with rice plants (Oryza sativa L.) were conducted to evaluate the effects of foliar applications of selenite (Se(IV)) and SeNPs on Se uptake, translocation, and speciation. Plant growth, chemical, and biochemical parameters were evaluated. Selenium accumulation and speciation were determined using inductively coupled plasma mass spectrometry (ICP-MS) and high-performance liquid chromatography coupled with ICP-MS (HPLC-ICP-MS). The results demonstrated that SeNP treatment did not adversely affect plant growth, grain yield, and oxidative stress or significantly increase the inorganic Se content in rice grains. From a nutritional perspective, grains biofortified with SeNPs had the potential to meet 100% of the recommended daily Se intake. Meanwhile, Se(IV) was more efficient for grain biofortification but increased the concentration of inorganic Se in rice grains by 141% compared to the control group. Regardless of the Se species applied, rice fertilization increased the proportion of selenomethionine while it reduced selenocysteine in grains. The treatment with SeNPs did not compromise the nutritional quality of rice grains but increased As content from 175 to 210 μg kg^–1, which remains below the maximum allowable limit of 350 μg kg^–1 for husked rice. The foliar application of SeNPs enables the production of Se-enriched rice with Se levels controlled within a safe range for human consumption and without significantly altering inorganic Se concentrations. This approach offers a viable strategy for addressing Se deficiency through biofortified rice.